There is a bit of face-spanking (slapping) in the more rougher/hardcore BDSM type movies. I think the idea is pretty hot where a top may already be dominating a bottom's ass, and then he slaps him too.

I've dominating a few guys who enjoy being slapped in the face. I agree that there is not enough porn with face slapping in it, but I love doing it. It sends such a clear message to the bottom that you are in control and their pain is you pleasure